Glossary

This section is informative.

A wide variety of terms are used in the realm of digital identity. While many definitions are consistent with earlier versions of SP 800-63, some have changed in this revision. Many of these terms lack a single, consistent definition, warranting careful attention to how the terms are defined here.

applicant: A subject undergoing the processes of identity proofing and enrollment.
applicant reference: A representative of the applicant who can vouch for the identity of the applicant, specific attributes related to the applicant, or conditions relative to the context of the individual (e.g., emergency status, homelessness).
approved cryptography: An encryption algorithm, hash function, random bit generator, or similar technique that is Federal Information Processing Standards (FIPS)-approved or NIST-recommended. Approved algorithms and techniques are either specified or adopted in a FIPS or NIST recommendation.
assertion: A statement from an IdP to an RP that contains information about an authentication event for a subscriber. Assertions can also contain identity attributes for the subscriber in the form of attribute values, derived attribute values, and attribute bundles.
attribute: A quality or characteristic ascribed to someone or something. An identity attribute is an attribute about the identity of a subscriber (e.g., name, date of birth, address).
attribute validation: The process or act of confirming that a set of attributes are accurate and associated with a real-life identity. See validation.
authenticate: See authentication.
authenticated protected channel: An encrypted communication channel that uses approved cryptography in which the connection initiator (client) has authenticated the recipient (server). Authenticated protected channels are encrypted to provide confidentiality and protection against active intermediaries and are frequently used in the user authentication process. Transport Layer Security (TLS) and Datagram Transport Layer Security (DTLS) [RFC9325] are examples of authenticated protected channels in which the certificate presented by the recipient is verified by the initiator. Unless otherwise specified, authenticated protected channels do not require the server to authenticate the client. Authentication of the server is often accomplished through a certificate chain that leads to a trusted root rather than individually with each server.
authentication: The process by which a claimant proves possession and control of one or more authenticators bound to a subscriber account to demonstrate that they are the subscriber associated with that account.
authentication assurance level (AAL): A category that describes the strength of the authentication process.
authenticator: Something that the subscriber possesses and controls (e.g., a cryptographic module or password) and that is used to authenticate a claimant’s identity. See authenticator type and multi-factor authenticator.
authenticity: The property that data originated from its purported source.
authoritative source: An entity that has access to or verified copies of accurate information from an issuing source such that a CSP has high confidence that the source can confirm the validity of the identity attributes or evidence supplied by an applicant during identity proofing. An issuing source may also be an authoritative source. Often, authoritative sources are determined by a policy decision of the agency or CSP before they can be used in the identity proofing validation phase.
authorize: A decision to grant access, typically automated by evaluating a subject’s attributes.
biometric reference: One or more stored biometric samples, templates, or models attributed to an individual and used as the object of biometric comparison in a database, such as a facial image stored digitally on a passport, fingerprint minutiae template on a National ID card, or Gaussian Mixture Model for speaker recognition.
biometric sample: An analog or digital representation of biometric characteristics prior to biometric feature extraction, such as a record that contains a fingerprint image.
biometrics: Automated recognition of individuals based on their biological or behavioral characteristics. Biological characteristics include but are not limited to fingerprints, palm prints, facial features, iris and retina patterns, voice prints, and vein patterns. Behavioral characteristics include keystroke cadence, the angle of holding a smartphone, screen pressure, typing speed, mouse or mobile phone movements, and gyroscope position, among others.
claimant: A subject whose identity is to be verified using one or more authentication protocols.
claimed identity: An applicant’s declaration of unvalidated and unverified personal attributes.
core attributes: The set of identity attributes that the CSP has determined and documented to be required for identity proofing and to provide services.
credential service provider (CSP): A trusted entity whose functions include identity proofing applicants to the identity service and registering authenticators to subscriber accounts. A CSP may be an independent third party.
credible source: An entity that can provide or validate the accuracy of identity evidence and attribute information. A credible source has access to attribute information that was validated through an identity proofing process or that can be traced to an authoritative source, or it maintains identity attribute information obtained from multiple sources that is checked for data correlation for accuracy, consistency, and currency.
digital identity: An attribute or set of attributes that uniquely describes a subject within a given context.
digital signature: An asymmetric key operation in which the private key is used to digitally sign data, and the public key is used to verify the signature. Digital signatures provide authenticity protection, integrity protection, and non-repudiation support but not confidentiality or replay attack protection.
disassociability: Enabling the processing of personal information or events without association to individuals or devices beyond the operational requirements of the system. [NISTIR8062]
enrollment: The process through which a CSP/IdP provides a successfully identity-proofed applicant with a subscriber account and binds authenticators to grant persistent access.
entropy: The amount of uncertainty that an attacker faces to determine the value of a secret. Entropy is usually stated in bits. A value with n bits of entropy has the same degree of uncertainty as a uniformly distributed n-bit random value.
Federal Information Processing Standards (FIPS): Standards for adoption and use by federal departments and agencies that are developed by NIST, a part of the U.S. Department of Commerce. FIPS address topics in information technology to achieve common levels of quality, security, and interoperability. FIPS documents are available online on the FIPS home page: https://www.nist.gov/itl/fips.cfm.
federation: A process that allows for the conveyance of identity and authentication information across a set of networked systems.
federation assurance level (FAL): A category that describes the process used in a federation transaction to communicate authentication events and subscriber attributes to an RP.
identifier: A data object that is associated with a single, unique entity (e.g., individual, device, or session) within a given context and is never assigned to any other entity within that context.
identity: See digital identity.
identity assurance level (IAL): A category that conveys the degree of confidence that the subject’s claimed identity is their real identity.

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identity evidence

Information or documentation that supports the real-world existence of the claimed identity. Identity evidence may be physical (e.g., a driver’s license) or digital (e.g., a mobile driver’s license or digital assertion). Evidence must support both validation (i.e., confirming authenticity and accuracy) and verification (i.e., confirming that the applicant is the true owner of the evidence).

identity proofing

The processes used to collect, validate, and verify information about a subject to establish assurance in the subject’s claimed identity.

identity provider (IdP)

The party in a federation transaction that creates an assertion for the subscriber and transmits the assertion to the RP.

identity resolution

The process of collecting information about an applicant to uniquely distinguish an individual within the context of the population that the CSP serves.

identity verification

See verification.

injection attack

An attack in which an attacker supplies untrusted biometric information or media into a program or process. For example, this could include injecting a falsified image of identity evidence, a forged video of a user, or a morphed image to defeat evidence validation technology or biometric and visual comparisons for user verification.

issuing source

An authority responsible for the generation of data, digital evidence (i.e., assertions), or physical documents that can be used as identity evidence.

knowledge-based verification (KBV)

A process of validating the knowledge of personal or private information associated with an individual for the purpose of verifying the claimed identity of an applicant. KBV does not include collecting personal attributes for the purposes of identity resolution.

manageability

Providing the capability for the granular administration of personal information, including alteration, deletion, and selective disclosure. [NISTIR8062]

natural person

A real-life human being, not synthetic or artificial.

network

An open communications medium, typically the internet, used to transport messages between the claimant and other parties. Unless otherwise stated, networks are assumed to be open and subject to active (e.g., impersonation, session hijacking) and passive (e.g., eavesdropping) attacks at any point between the parties (e.g., claimant, verifier, CSP, RP).

non-repudiation

The capability to protect against an individual falsely denying having performed a particular transaction.

one-to-one (1:1) comparison

The process in which a biometric sample from an individual is compared to a biometric reference to produce a comparison score.

online attack

An attack against an authentication protocol in which the attacker either assumes the role of a claimant with a genuine verifier or actively alters the authentication channel.

online service

A service that is accessed remotely via a network, typically the internet.

personal information

Information that can be used to distinguish or trace an individual’s identity, either alone or when combined with other information that is linked or linkable to a specific individual.

practice statement

A formal statement of the practices followed by parties in an authentication process (e.g., CSP or verifier). It usually describes the parties’ policies and practices and can become legally binding.

predictability

Enabling reliable assumptions by individuals, owners, and operators about personal information and its processing by an information system. [NISTIR8062]

presentation attack

Presentation to the biometric data capture subsystem with the goal of interfering with the operation of the biometric system.

presentation attack detection (PAD)

Automated determination of a presentation attack. A subset of presentation attack determination methods (i.e., liveness detection) involves the measurement and analysis of anatomical characteristics or voluntary or involuntary reactions to determine whether a biometric sample is being captured from a living subject that is present at the point of capture.

Privacy Impact Assessment (PIA)

A method of analyzing how personal information is collected, used, shared, and maintained. PIAs are used to identify and mitigate privacy risks throughout the development life cycle of a program or system. They also help ensure that handling information conforms to legal, regulatory, and policy requirements regarding privacy.

private key

A cryptographic key used with a public-key cryptographic algorithm that is uniquely associated with an entity and is not made public. In an asymmetric-key (public-key) cryptosystem, the private key has a corresponding public key. Depending on the algorithm, the private key may be used to:

Compute the corresponding public key,
Compute a digital signature that may be verified by the corresponding public key,
Decrypt keys that were encrypted by the corresponding public key, or
Compute a shared secret during a key-agreement transaction.

process assistant

An individual who provides support for the proofing process but does not support decision-making or risk-based evaluation (e.g., translation, transcription, or accessibility support).

processing

An operation or set of operations performed on personal information that can include, but is not limited to, the collection, retention, logging, generation, transformation, use, disclosure, transfer, or disposal of personal information. [NISTIR8062]

proofing agent

An agent of the CSP who is trained to attend identity proofing sessions and can make limited risk-based decisions, such as physically inspecting identity evidence and comparing the applicant to the identity evidence.

pseudonym

A name other than a legal name.

pseudonymity

The use of a pseudonym to identify a subject.

pseudonymous identifier

A meaningless but unique identifier that does not allow the RP to infer anything regarding the subscriber but that does permit the RP to associate multiple interactions with a single subscriber.

public key

A cryptographic key used with a public-key cryptographic algorithm that is uniquely associated with an entity and that may be made public. In an asymmetric-key (public-key) cryptosystem, the public key has a corresponding private key. The public key may be known by anyone and, depending on the algorithm, may be used to:

Verify a digital signature that was generated using the corresponding private key,
Encrypt keys that can be decrypted using the corresponding private key, or
Compute a shared secret during a key-agreement transaction.

public-key certificate

A digital document issued and digitally signed by the private key of a certificate authority that binds an identifier to a subscriber’s public key. The certificate indicates that the subscriber identified in the certificate has sole control of and access to the private key. See also [RFC5280].

public-key infrastructure (PKI)

A set of policies, processes, server platforms, software, and workstations used to administer certificates and public-private key pairs, including the ability to issue, maintain, and revoke public-key certificates.

registration

See enrollment.

relying party (RP)

An entity that relies on a verifier’s assertion of a subscriber’s identity, typically to process a transaction or grant access to information or a system.

remote

A process or transaction that is conducted through connected devices over a network rather than in person.

resolution

See identity resolution.

risk assessment

The process of identifying, estimating, and prioritizing risks to organizational operations (i.e., mission, functions, image, reputation), organizational assets, individuals, and other organizations that result from the operation of a system. A risk assessment is part of risk management, incorporates threat and vulnerability analyses, and considers mitigations provided by security controls that are planned or in place. It is synonymous with “risk analysis.”

risk management

The program and supporting processes that manage information security risk to organizational operations (i.e., mission, functions, image, reputation), organizational assets, individuals, and other organizations and that include (i) establishing the context for risk-related activities, (ii) assessing risk, (iii) responding to risk once determined, and (iv) monitoring risk over time.

RP subscriber account

An account established and managed by the RP in a federated system based on the RP’s view of the subscriber account from the IdP. An RP subscriber account is associated with one or more federated identifiers and allows the subscriber to access the account through a federation transaction with the IdP.

Senior Agency Official for Privacy (SAOP)

Person responsible for ensuring that an agency complies with privacy requirements, manages privacy risks, and considers the privacy impacts of all agency actions and policies that involve personal information.

session

A persistent interaction between a subscriber and an endpoint, either an RP or a CSP. A session begins with an authentication event and ends with a session termination event. A session is bound by the use of a session secret that the subscriber’s software (e.g., browser, application, OS) can present to the RP to prove association of the session with the authentication event.

social engineering

The act of deceiving an individual into revealing sensitive information, obtaining unauthorized access, or committing fraud by associating with the individual to gain confidence and trust.

subject

A person, organization, device, hardware, network, software, or service. In these guidelines, a subject is a natural person.

subscriber

An individual enrolled in the CSP identity service.

subscriber account

An account established by the CSP for each subscriber enrolled in its identity service that contains information about the subscriber and a record of any authenticators registered to the subscriber.

supplemental controls

Controls that may be added to address specific threats or attacks in addition to those controls specified in the assurance levels in these guidelines.

synthetic identity fraud

The use of a combination of personal information to fabricate a person or entity to commit a dishonest act for personal or financial gain.

system of record (SOR)

A collection of records that contain information about individuals and are under the control of an agency. The records can be retrieved by the individual’s name, an identifying number, a symbol, or other identifier.

System of Records Notice (SORN)

A notice that federal agencies publish in the Federal Register to describe their system of record.

transaction

See digital transaction.

trust agreement

A set of conditions under which a CSP, IdP, and RP are allowed to participate in a federation transaction to establish an authentication session between the subscriber and the RP.

trust anchor

A public or symmetric key that is trusted because it is built directly into hardware or software or securely provisioned via out-of-band means rather than because it is vouched for by another trusted entity (e.g., in a public-key certificate). A trust anchor may have name or policy constraints that limit its scope.

trusted referee

An agent of the CSP who is trained to make risk-based decisions regarding an applicant’s identity proofing case when that applicant is unable to meet the expected requirements of a defined IAL proofing process.

usability

The extent to which a product can be used by specified users to achieve specified goals with effectiveness, efficiency, and satisfaction in a specified context of use. [ISO/IEC9241-11]

validation

The process or act of checking and confirming that the evidence and attributes supplied by an applicant are authentic, accurate, and associated with a real-life identity. See attribute validation.

verification

The process or act of confirming that the applicant undergoing identity proofing holds the claimed real-life identity represented by the validated identity attributes and associated evidence. Synonymous with identity verification.

verifier

An entity that confirms the claimant’s identity by verifying the claimant’s possession and control of one or more authenticators using an authentication protocol. To do this, the verifier needs to confirm the binding of the authenticators with the subscriber account and check that the subscriber account is active.